Fuel burners

ABSTRACT

A dual fuel burner assembly for a gas turbine engine has a fuel nozzle consisting of a central member in which ducts for the flow of liquid and gaseous fuel and a supply of air are formed and a shroud member. The outlets of the liquid fuel ducts communicate with the air supply ducts and the shroud member has a flared end formed with a number of equi-spaced slots which are aligned with the outlets of the gaseous fuel ducts. A supply of air is arranged to flow through the slots to stabilise the flow of gaseous fuel at low fuel flows. A heat shield is attached to the downstream face of the central member and the gap between the heat shield and the central member is in communication with the air supply ducts so that air can flow around the heat shield to prevent carbon deposition.

United States Patent 91 Carlisle et al.

[ Jan. 29, 1974 1 FUEL BURNERS [75] inventors: Denis Richard Carlisle, Risley; John Joseph Nichols, Longbridge, both of England [73] Assignee: The Secretary of State for Defense,

in Her Britannic Majestys Government of the United Kingdom of Great Britain and Northern Ireland, Whitehall, London, England 22 Filed: Jan. 31, 1972 21 Appl. No.: 221,954

[30] Foreign Application Priority Data Feb. 2, 1971' Great Britain 3657/71 [52] US. Cl 60/39.74 B [51] Int. Cl F02c 7/22, F02g 3/00 [58] Field of Search 60/3974 R [56] References Cited UNITED STATES PATENTS 3,236,279 2/1966 Beyer 60/3974 R 3,724,207 4/1973 Johnson 60/39.74 R

A dual fuel burner assembly for a gas turbine engine has a fuel nozzle consisting of a central member in which ducts for the flow of liquid and gaseous fuel and a supply of air are formed and a shroud member. The outlets of the liquid fuel ducts communicate with the air supply ducts and the shroud member has a flared end formed with a number of equi-spaced slots which are aligned with the outlets of the gaseous fuel ducts. A supply of air is arranged to flow through the slots to stabilise the flow of gaseous fuel at low fuel flows.

A heat shield is attached to the downstream face of the central member and the gap between the heat shield and the central member is in communication with the air supply ducts so that air can flow around the heat shield to prevent carbon deposition.

3 Claims, 4 Drawing Figures PATENTEDJAH29 mm 3788 067 SHEET 2 OF 2 FUEL BURNERS This invention relates to fuel burners and is concerned with fuel burners for gas turbine engines which are capable of operating on two or more different fuels, i.e., a liquid fuel and a gaseous fuel.

According to the present invention there is provided a burner assembly for a gas turbine engine, the assem-' bly including a fuel nozzle having a plurality of ducts arranged to receive liquid fuel and a plurality of ducts arranged to receive a gaseous fuel, a supply of air being arranged to impinge upon the gaseous fuel leaving the gaseous fuel ducts.

The fuel nozzle may comprise a central member and a shroud member, the shroud member having a number of axial slots which aligned in the outlets of the gaseous fuel ducts.

The liquid and gaseous fuel ducts may be formed in the central member and may be arranged alternately around the circumference of the central member.

The central member may have a plurality of liquid fuel supply ducts, at least one of which is arranged to be coaxial with the central member, the remaining supply ducts being in communication with the liquid fuel ducts.

The liquid supply ducts comprise two portions, one portion extending axially parallel to the axis of the central member, the other portion extending radially and in a downstream direction connecting the liquid fuel supply ducts with the liquid fuel ducts.

The downstream ends of the central member and the shroud may be flared outwardly to give the desired fuel spray angle.

Preferably the flared end of the shroud is formed with air slots which are aligned with the outlets of the gaseous fuel ducts, so that the air can impinge upon the gaseous fuel passing out of the gaseous fuel ducts.

The shroud may also have further air supply slots which are in communication with the liquid fuel ducts in the central member to ensure substantially complete atomisation of the liquid fuel at all fuel flows.

Preferably, a primary fuel nozzle and primary fuel injector are retained in the central member, the primary fuel nozzle being secured to the central member and the primary fuel injector being biased by a spring against a shoulder on the primary fuel nozzle.

The primary fuel injector may have a central bore in communication with the central liquid fuel supply duct in the central member, the bore being in communication with at least two radially extending outlet ducts,-

primary fuel being arranged to leave said two ducts and impinge against a frusto-conical deflecting face formed on the primary fuel nozzle.

A heat shield may be secured to the downstream end of the central member and form a recess in combination with the central member, the recess being in communication with the liquid fuel ducts so that air can FIG. 3 is a section through the combustion apparatus shown in FIG. 2 and FIG. 4 is a composite end view showing a quarter section A, a quarter end view and a half section B.

In the drawings, FIG. 1 shows a gas turbine engine 10 having compressor means 12, combustion apparatus 14 and turbine means 16, the combustion apparatus comprising a number of circumferentially arranged combustion chambers 18, each having a burner assembly 20 mounted on a burner arm 22.

Referring now more particularly to FIGS. 3 and 4, the burner arm has three ducts 24, 26 and 28 for the supply of fuel, the ducts 24 and 26 being for liquid fuel and the duct 28 for gaseous fuel. The duct 24 is for the flow of primary fuel and duct 26 is for the flow of main fuel. The burner assembly is screwed onto the arm 22 at 30 and comprises a main liquid fuel nozzle 32 having shroud 34 with a flared skirt 36, a primary fuel nozzle 38, a primary fuel injector 40 and a heat shield 42.

The fuel nozzle 32 has eight circumferentially arranged equi-spaced axial ducts 44 which are connected to the main fuel duct 26, the ducts 44 being in communication with eight corresponding fuel jets 46. The main fuel can then pass into circumferentially spaced axial ducts 48 which are formed between the nozzle 32 and the shroud 34. A central duct 50 for the flow of primary fuel to the injector 40 is provided in the nozzle 32 and is connected to the duct 24 in the arm 22. Eight equi-spaced axial ducts 58 are machined in the nozzle 32 for the flow of a gaseous fuel and each of the slots 52 are connected to the duct 28 by means of a manifold 54 and drillings 56. The further eight axial ducts 58 are located between the ducts 48, one duct 58 being located between two adjacent ducts 48. Eight slots 60 are machined in the shroud 34 so that high pressure air can flow into the ducts 58 and atomise the main fuel flowing out of the jets 46. Eight slots 62 are machined in the skirt 36 for the flow of high pressure air which is used to narrow the angle of the gaseous fuel at low gaseous fuel flow values. Eight apertures 64 connect the ducts 58 with a recess 66 which is formed in the downstream end of the nozzle 32.

The primary fuel nozzle 38 is screwed into the main fuel nozzle at 68 and retains the primary fuel injector 40 which is biased in the downstream direction by a coil spring 70. A frusto-conical deflecting surface 69 is formed on the downstream face of the nozzle 38. The primary fuel injector 40 has a central bore 72 which is in communication with the duct 24 and two jets 74 which are connected with the bore 72. Fuel passing out of the jets 74 is arranged to impinge against a frustoconical surface formed on the primary nozzle 38. The operation of the primary fuel nozzle and injector are as described in the copending U.S. application Ser. No. 221,953 filed Jan. 31, 1972 by Denis Richard Carlisle and assigned to the same assignee (now abandoned).

The heat shield 42 is attached to the main fuel nozzle 32 by means of two screws 76 and the heat shield is keyed to the injector 38 by means (not shown) to prevent rotation of the injector.

In use, primary fuel passes out of the ducts 74 and impinges against the deflecting surface to form two locally enriched zones of fuel. This particularly ensures that weak extinction does not occur and that anti-smoke requirements are met. This particular portion of the burner assembly is described in detail in the aforementioned U.S. application Ser. No. 221,953.

The main fuel passes out of the jets 46 into the ducts 58 where it is atomised by the high pressure air which flows into the duct through the slots 60. This arrangement is particularly suitable for atomising the main fuel flow when the flow value is low. The high pressure air also flows into the recess 66 and around the heat shield 42 to prevent the deposition of carbon.

When it is required to run the engine on gaseous fuel, the liquid fuel supply is shut off and gaseous fuel is allowed to flow through the ducts 48. During normal running the high pressure air which flows through the slots 62 does not have any significant effect on the gaseous arranged around the periphery of said central member and all of said ducts being at substantially the same radial distance from the center of said central member, and a shroud member surrounding the central member, the shroud member having a plurality of slots aligned with the outlets of the gaseous fuel ducts, the slots extending longitudinally in a direction parallel with the centerline of the nozzle.

2. A fuel nozzle as claimed in claim 1 in which the downstream ends of the central member and the shroud member are flared outwardly to give the desired spray angle, the slots being formed in the flared end of the shroud.

3. A fuel nozzle as claimed in claim 1 in which a heat shield is attached to the downstream end of the nozzle and forms a recess in combination with the central member of the nozzle, and in which air supply ducts are formed in the central member in communication with the recess.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,788,067 Dated a y 9 197 Patent No.

) Denis Richard Carlisle and John Joseph Nichols Inventor(s It is certified that error appears in the above-identified patent corrected as shown below:

and that said Letters Patent are hereby In the front page format ofche above-identified Patent, please correct [.30] to read as follows:

--[30] Foreign Application Priority Date.

Feb. 2, 1971 Great Britain. .'.3655/71-- Signed and sealed this 21st day of May 1974.

(SEAL) Attest: I EDWARD M.FLETCHER,JR. I c. MARSHALL DANN Attesting Officer A a Commissioner of Patents USCOMM-OC 603764 69 I 5. GOVIINMKNI 'IIN'IIO 0"! I"! 0-3864) FORM PO-\ 050 (10-69) 

1. A fuel burner nozzle for a gas turbine engine, the nozzle including a central member having a plurality of ducts arranged to receive liquid fuel and a plurality of ducts arranged to receive a gaseous fuel, said gaseous fuel ducts and said liquid fuel ducts being alternately arranged around the periphery of said central member and all of said ducts being at substantially the same radial distance from the center of said central member, and a shroud member surrounding the central member, the shroud member having a plurality of slots aligned with the outlets of the gaseous fuel ducts, the slots extending longitudinally in a direction parallel with the centerline of the nozzle.
 2. A fuel nozzle as claimed in claim 1 in which the downstream ends of the central member and the shroud member are flared outwardly to give the desired spray angle, the slots being formed in the flared end of the shroud.
 3. A fuel nozzle as claimed in claim 1 in which a heat shield is attached to the downstream end of the nozzle and forms a recess in combination with the central member of the nozzle, and in which air supply ducts are formed in the central member in communication with the recess. 